you have to use use modulename inside your .pl file.
if the .pm file is in the other directory, mention that path in the @INC variable, or use 'use lib' pragma, or -I option to the interpreter.
you can call that routine like classname::routinename as plain
with OO you can call classname->routinename
see my earlier post Re^3: A Class inside a Perl script?

Vivek
-- In accordance with the prarabdha of each, the One whose function it is to ordain makes each to act. What will not happen will never happen, whatever effort one may put forth. And what will happen will not fail to happen, however much one may seek to prevent it. This is certain. The part of wisdom therefore is to stay quiet.